In recent years, there has been an increase in empirical literature regarding how and why neuroscience and genetics research on behavior may influence criminal punishment. This dissertation aims to add to this growing body of literature specifically on types of evidence and aspects of sentencing and punishment that have not yet been studied. This dissertation consists of three papers that examine how the presentation of biological evidence in court or knowledge of the biological influences to behavior may act as extra-legal and discretionary factors in sentencing. The first paper, utilizing a multi-factorial experiment with the death-qualified jury-eligible public, examines how biological risk factors for criminality might affect views on capital sentencing. Results suggest that the general presentation of evidence on biological risk factors may not impact views on death penalty support or cruel and unusual punishment, but it may significantly impact perceptions of moral responsibility and future dangerousness. The second paper, utilizing a multi-factorial experiment with a lay public sample, examines how psychiatric labels, and having diagnoses biologically “labelled,” affect sentencing beliefs. Results show that psychiatric labels can lead to significant non-punitive effects on sentencing, as mediated by reduced stigmatization regarding lack of treatability, social acceptance, and personal responsibility. Biological “labelling” may not significantly affect sentencing, apart from Pedophilic Disorder. The third paper, utilizing qualitative interviews with Pennsylvania state judges and grounded theory analysis, develops a model that illuminates a process by which judicial stereotyping associated with genetic essentialist biases toward mental disorders may negatively affect judges’ views regarding the sentencing of offenders with psychiatric diagnoses. Data suggest that judges exhibit stereotyping behavior by linking the relationships between genetic essentialist biases (immutability, informativeness, uniformity) and types of stigmatization (pessimism, dangerousness, family stigma), leading to judges’ negative views on the punishment of such offenders particularly with regard to incapacitation and deterrence. Together, the findings in this dissertation advance our understanding on if and how different types of biological research on behavior may practically and philosophically influence discretion in sentencing. Such understanding can help to anticipate the effects of neuroscience and genetics research as discretionary and extra-legal factors in sentencing moving forward.